Architecture, deformation style and petrophysical properties of growth fault systems: the Late Triassic deltaic succession of southern Edgeøya (East Svalbard)

Abstract

The Late Triassic outcrops on southern Edgeøya, East Svalbard, allow a multiscale study of syn-sedimentary listric growth faults located in the prodelta region of a regional prograding system. At least three hierarchical orders of growth faults have been recognized, each showing different deformation mechanisms, styles and stratigraphic locations of the associated detachment interval. The faults, characterized by mutually influencing deformation envelopes over space-time, generally show SW-to SE-dipping directions, indicating a counter-regional trend with respect to the inferred W-NW directed progradation of the associated delta system. The down-dip movement is accommodated by polyphase deformation, with the different fault architectural elements recording a time-dependent transition from fluidal-hydroplastic to ductile-brittle deformation, which is also conceptually scale-dependent, from the smaller-(3rd order) to the larger-scale (1st order) end-member faults respectively. A shift from distributed strain to strain localization towards the fault cores is observed at the meso to microscale (<1 mm), and in the variation in petrophysical parameters of the litho-structural facies across and along the fault envelope, with bulk porosity, density, pore size and microcrack intensity varying accordingly to deformation and reworking intensity of inherited structural fabrics. The second-and third-order listric fault nucleation points appear to be located above blind fault tip-related monoclines involving cemented organic shales. Close to planar, through-going, first-order faults cut across this boundary, eventually connecting with other favourable lower-hierarchy fault to create seismic-scale fault zones similar to those imaged in the nearby offshore areas. The inferred large-scale driving mechanisms for the first-order faults are related to the combined effect of tectonic reactivation of deeper Palaeozoic structures in a far field stress regime due to the Uralide orogeny, and differential compaction associated with increased sand sedimentary input in a fine-grained, water-saturated, low-accommodation, prodeltaic depositional environment. In synergy to this large-scale picture, small-scale causative factors favouring second-and third-order faulting seem to be related to mechanicalrheological instabilities related to localized shallow diagenesis and liquidization fronts.--

Jurassic to Early Cretaceous basin configuration(s) in the Fingerdjupet Subbasin, SW Barents Sea

“…described Upper Triassic growth packages on N-S to NNE-SSW striking faults in the Fingerdjupet Subbasin, indicating Late Triassic fault reactivation. In the Hammerfest Basin and on Edgeøya and Hopen (islands), south and north on the Barents Shelf, respectively, E-W striking faults were active in the latest Triassic (Anell et al, 2013;Anell, Faleide and Braathen, 2016;Ogata et al, 2018).…”

Mesozoic‐Cenozoic Regional Stress Field Evolution in Svalbard

“…Listric faults, wedge shaped fill geometries, and exposed structures indicate a detachment exists approximately at the base of the Tschermakfjellet shales or within the top of the Botneheia Formation, probably due to early cementation of the Botneheia Formation shales (Krajewski, ) that provided a strength contrast. Significant soft‐sediment deformation, including sandstone dikes, is consistent with syn‐sedimentary faulting, but the detachment level also shows brittle features and distinctive mineralization (i.e., cone‐in‐cone calcite growths) indicating faulting occurred during early lithification (Maher et al, ; Ogata et al, ). Conjugate fault planes, fault striae, and the rotation of strata (Figures a–c) show significant dispersion, but all indicate a dominant general NE‐SW extension for the Kvalpynten area.…”

“…Syn‐sedimentary Triassic normal faults on Edgeøya and Hopen (Braathen, Midtkandal, et al, ; Maher et al, ; Ogata et al, ; Osmundsen et al, ; Smyrak‐Sikora et al, ), and offshore (Anell et al, ), provide potential insight into crustal stresses at that time. These faults can be separated into two groups, thick‐skinned versus thin‐skinned, a division introduced by Anell et al () and adhered to herein.…”

“…Distributed normal faulting in the monocline limb indicates extension, consistent with the development of a tri‐shear zone (Fossen, ) above a fault tip. Other clear examples of syn‐sedimentary movement along these faults exist on Edgeøya (Ogata et al, ; Osmundsen et al, ; Smyrak‐Sikora et al, ).…”

“…Anell et al () and Osmundsen et al () provide more detailed description, arguing that there was a tectonic influence. Braathen, Midtkandal, et al () argue that differential delta‐front compaction was involved, a model that Ogata et al () and Smyrak‐Sikora et al (Smyral‐Sikora et al, ) elaborate on.…”